The voice detector in the dog brain (left) is in a location close to the detector region in the human brain (right).

Courtesy of Current Biology

Originally published on February 25, 2014 6:47 am

A paw on the leg. A nose nuzzling against your arm. Maybe even a hop onto your lap.

Dogs always seem to know when you're upset and need extra love, even though they hardly understand a word of what you say. How can that be?

Our four-legged friends have a little patch of their brain devoted to deciphering emotions in human and dog voices, scientists reported Thursday in the journal Current Biology.

And the neural circuitry acts surprisingly like the voice-detection device found in people's brains. The happier the barks or giggles, the more that brain region lights up. The sadder the growls or whines, the less it responds.

To find the brain region, Andics and his team first had to accomplish the seemingly impossible: Get 11 pooches to lie motionless inside an MRI brain scanning machine for nearly 10 minutes at a time, all while listening to nearly 200 people and dog noises.

"They are happy volunteers in the scanner — you should just see it! They really are!" Andics tells Shots.

Other researchers have gotten a few dogs to sit still long enough in an MRI machine to analyze their brain activity. But the feat has never been accomplished with so many dogs and for such long periods of time.

"We really have no clue about what's going on in the dog's brain," Andics says. "Now we can start to look at how our best friend looks at us and figure out what makes our alliance and communication with them so strong."

Back in the late 1990s, Canadian scientists identified a part of the human brain devoted to recognizing people's voices. The so-called voice area doesn't process words or sentences. Rather, it figures out all the other information packed into sounds. For instance, who's the person speaking? How is he feeling? Is she being snarky or serious? Silly or sardonic?

Andics and his team wanted to see if dogs had an analogous region in their brains. But how do you get an energetic border collie to sit still long enough to perform the experiment? "If they move more than a few millimeters, we have to start the scans again," Andics says.

He and his team started off with standard training methods: heaps of treats, praise and love. But what really did the trick, Andics says, was brewing up a little bit of jealousy among the dogs.

"We'd put an experienced dog up in the scanner, and he'd be up there sitting still," Andics says. "Then we'd bring into the room a less experienced dog. And he'd get so jealous! He just wanted to be on the scanner bed like the other dog. It became the place of happiness."

After about 20 training sessions apiece, Andics and his team had a pack of border collies and Labrador and golden retrievers all ready for their experiments.

They put headphones on each dog and let them listen to three types of sounds: human voices, doggy voices and environmental noises, such as a phone ringing or a hammer hitting a nail. The team then looked to see which parts of the brain responded.

Lo and behold, just as with humans, the dogs have a little patch of neurons that light up most strongly when they hear voices of their own species — other dogs barking, growling or whining.

There also was a region that was sensitive to emotional tones in both human and dog voices. And that area was in the same location as the one found in people — right in the back of the brain near the ears.

"When you looked at how dogs respond to emotional cues in sounds, it's very similar to how humans respond," Andics says. "It's in the same brain region ... and is stronger with positive vocalizations than negative ones."

So how do our furry companions tell a happy giggle from a sad sigh?

"Like people, dogs use simple acoustic parameters to extract out the feelings from a sound," Andics says. "For instance, when you laugh, 'Ha ha ha,' it has short, quick pieces. But if you make the pieces longer, 'Haaaa, haaaa, haaaa,' it starts to sound like crying or whining. This is what people — and dogs — pay attention to."

And one way Fido knows you need that extra kiss after a long day at work.